Choline acetyltransferase catalyzes the biosynthesis of acetylcholine, an alleged neurotransmitter agent. The enzyme has been purified to electrophoretic homogeneity by a combination of classical techniques and affinity chromatography. Studies on the mechanism of action of the enzyme including identification of the amino acid residues involved in catalysis are underway. The physical properties including molecular weight, sedimentation ceofficient, Stokes radius and conditions for stabilizing activity are also proposed. Studies on the mechanism of interaction of the regulatory and catalytic subunits of bovine brain cyclic AMP-dependent protein kinase are also proposed. This enzyme may play a fundamental role in chemical neuro-transmission by regulating neurotransmitter biosynthesis and by controlling membrane permeability. BIBLIOGRAPHIC REFERENCES: Witt, J.J. and Roskoski, R. Jr., Rapid Protein Kinase Assay using Phosphocellulose Paper Absorption. (1975) Anal. Biochem. "66", 253-258. Roskoski, R. Jr., Schmid, P.G., Mayer, H.E. and Abboud, F.M., In Vitro Acetylcholine Biosynthesis in Normal and Failing Guinea Pig Hearts. (1975) Circulation Research "36", 547-552.